Update (5/15/09): I have working binaries of the latest code available in my PPA repository. Directions for adding it to your package manager are available here.
Here's how the live preview looks. You can really get in there and see the direct impact of your changes. This leads to better cropping and a better sense for your end product. (this is my Mac x-forwarding GHB from my Ubuntu box. As you can see, the live previews even work through that):
For those of you who wish to compile on your own hardware (recommended for those with newer Core 2 Duo CPUs), the process is exactly the same as my previous SVN instructions, except for the addition of 2 new dependencies: libgstreamer0.10-dev and libgstreamer-plugins-base0.10-dev. I've updated the instructions there to reflect the change.